(a) Field of the Invention
The present invention relates to an automatic transmission of a vehicle, and more particularly, to a clutch (or a brake) of an automatic transmission.
(b) Background
Generally, a clutch mounted to an automatic transmission operates when an automatic transmission is converted to a target shift-speed during a shifting operation.
Such a conventional clutch of an automatic transmission includes a rear clutch, a front clutch, etc.
As shown in FIG. 1, a conventional clutch (or brake) includes a piston 30, a plurality of main plates 10, a plurality of friction plates 20 disposed alternatively to the plurality of main plates 10, and a reaction plate 40. The plurality of main plates 10 include a first, second, and third main plates 11, 12, and 13 that are sequentially arranged, and the plurality of friction plates 20 include a first, second, and third friction plates 21, 22, and 23 that are sequentially arranged.
Accordingly, when hydraulic pressure is supplied to the piston 30, the main plates 10 move so as to contact the friction plates 20, and shifting operation is consequently performed at a target shift-speed. On the other hand, when the hydraulic pressure is released from the piston 30, the main plates 10 become disjointed from the friction plates 20 by restoring force created by the reaction plate 40, and operational elements are consequently released.
However, as shown in FIG. 1, since the piston 30 includes a convex portion 31 that is convex toward the first friction plate 21, the space between the first friction plate 21 having a linear configuration and the convex portion 31 of the piston 30 becomes narrower in one end portion of the plate. Therefore, when the piston 30 is operated by hydraulic pressure, interference between the piston 30 and the first friction plate 21 can be induced. Such interference can eventually shorten the lifetime of the piston 30 and friction plates 20, and it can disturb proper shifting operation at a target shift-speed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.